merb_form.html.erb

form.html

<% @pos.each |purchase_order| do %>  
  <%= form_for(purchase_order, :action => url(:create_po_purchasing_shopping_lists)) do %>
    <%= hidden_field :name => "counter", :value => count %>
      <%= partial 'purchasing/purchase_orders/basic_form', :po => po %>
      <button class="positive" type="submit">
         <img alt="create" src="/images/icons/tick.png"></img>
         Create
      </button>
  <% end =%>
<% end %>